Synthesis of a Molecularly Imprinted Polymer for the Solid-phase Extraction of Betulin and Betulinic Acid from Plane Bark

Plant extracts are usually complex mixtures of various polarity compounds and their study often includes a purifi cation step, such as solid-phase extraction (SPE), to isolate interest compounds prior analytical investigations. Molecularly imprinted polymers (MIPs)are a new promising type of SPE material which off er tailor-made selectivity for the extraction of trace active components in complex matrices. Numerous specifi c cavities that are sterically and chemically complementary of the target molecules, are formed in imprinted polymers. A molecularly imprinted polymer (MIP)was synthesised in order to trap a specifi c class of triterpene, including betulin and betulinic acid from a methanolic extract of plane bark. Methodology - Imprinted polymers were synthesised by thermal polymerisation of betulin as template, methacrylic acid (MAA)or acrylamide (AA)as functional monomer, ethylene glycol dimethacrylate as crosslinking agent and chloroform as porogen. Afterwards, MAA- and AA-MIPs were compared with their non-imprinted polymers (NIPs)in order to assess the selectivity vs betulin and its derivatives. Recovered triterpenes were analysed by HPLC during MIP-SPE protocol. Results - After SPE optimisation, the MAA-imprinted polymer exhibited highest selectivity and recovery (better than 70